1. Field of Invention
The present invention is directed generally to image-guided medical procedures, and more particularly, to systems and methods for the storage and geometric measurement of instrument trajectories used in image-based surgical guided navigation systems.
2. Description of the Related Art
Image based surgical techniques have been used with success in aiding physicians for performing a wide variety of delicate surgical procedures. These procedures are typically used when the visualization of a surgical tool could be obscured by a patient""s anatomy, or when the surgical tool is visible but the patient""s anatomy may be difficult to visualize in three dimensions. Such procedures include, for example, spinal implant placement, the alignment of broken bone fragments, and the fixation of bone fractures. Prior art techniques to accurately position a surgical instrument have included the use of x-ray images to localize its position. Through the repeated acquisition of x-ray images during the procedure, real-time placement of the instrument relative to the patient""s anatomy can be displayed. More recently, virtual fluoroscopically-based surgical navigation systems have been employed to track an instrument trajectory and superimpose its representation onto pre-acquired images without requiring x-rays to be repeatedly taken during the actual surgical procedure.
In many situations, a surgeon would like to create a static visual reference using the real-time and generally instantaneous instrument trajectory displayed by the surgical navigation system as the instrument progresses in the general direction of a selected, desired path. For example, some procedures require the serial placement of several implants which must be placed in a precise relative geometry. Currently, the surgeon must reacquire a new set of images after each implant is placed to properly determine the trajectory of the subsequent implant. This can be a time consuming process which increases the amount of radiation exposure to the patient and operating room personnel.
Other situations may require the surgeon to make accurate geometric measurements of a patient""s anatomy. For example, some surgical procedures require the precise removal of a specific amount of bone taken in the shape of a wedge. In order to determine this amount, an angular measurement of the bone at the surgical site would assist in this procedure. Another example would be in allowing the surgeon to make distance measurement between bone implant sites to ensure proper implant placement. In light of the foregoing, there is a need for the ability to save surgical instrument trajectories and have the capability to perform measurements thereon.
The present invention is directed generally to image guided medical procedures, and, particularly, to medical procedures involving the tracking of surgical instruments. More specifically, the present invention is directed to a device and method for storing instrument trajectories.
To achieve these objects and other advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention is directed to an apparatus and method for the storage of trajectories and measurements which may be performed thereon for use in conjunction with image-guided surgical navigation systems.
In one aspect of the invention, an instrument trajectory is tracked in real-time by a surgical navigation system. An icon representing this real-time trajectory is overlaid on one or more pre-acquired images of the patient. At the surgeon""s command, the navigation system can store the trajectory of the instrument and, if desired, create a static icon representing the saved trajectory for display on each pre-acquired image. The icon representing the stored trajectory is simultaneously displayed with the real-time trajectory""s icon so the surgeon may visually compare them. The surgeon has the option of saving additional trajectories by reissuing the storage command.
In another aspect of the invention, the surgeon may measure angles between pairs of any two trajectories. The angles are computed in the plane of the image, and are, therefore, computed separately for each image displayed. One option is to compute one or more angles between the real-time trajectory and saved trajectories. These angles are preferably computed and displayed on each pre-acquired image. As the real-time trajectory changes, the displayed values are preferably updated in each image in real-time. Another option is to measure one or more angles between pairs of any two stored trajectories. As with the prior option, these angles could be computed and displayed separately for each image.
In yet another aspect of the invention, three dimensional distances between pairs of points defined by one or more sets of two trajectories can be computed and displayed. One option is to measure the distance between the real-time trajectory and one or more saved trajectories. These measurements would be computed in real-time and updated on the display as the real-time trajectory varies. Another option would be computing and displaying distances between pairs of points defined by one or more sets of two user-selected stored trajectories. For either of these two options, the defined points may be represented by the tip of each trajectory as computed by the system, or may be defined by a user-selected extension projected from the trajectory""s tip.
Preferably, the invention can overcome the problems of the prior art by providing the surgeon with the visual reference and measurement information required for some surgical procedures.
Both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.